- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO

# NAME

EVP_PKEY_copy_parameters, EVP_PKEY_missing_parameters, EVP_PKEY_cmp_parameters, EVP_PKEY_cmp - public key parameter and comparison functions

# SYNOPSIS

     #include <openssl/evp.h>

     int EVP_PKEY_missing_parameters(const EVP_PKEY *pkey);
     int EVP_PKEY_copy_parameters(EVP_PKEY *to, const EVP_PKEY *from);

     int EVP_PKEY_cmp_parameters(const EVP_PKEY *a, const EVP_PKEY *b);
     int EVP_PKEY_cmp(const EVP_PKEY *a, const EVP_PKEY *b);

# DESCRIPTION

The function `EVP_PKEY_missing_parameters()` returns 1 if the public key parameters of pkey are missing and 0 if they are present or the algorithm doesn't use parameters.

The function `EVP_PKEY_copy_parameters()` copies the parameters from key from to key to. An error is returned if the parameters are missing in from or present in both from and to and mismatch. If the parameters in from and to are both present and match this function has no effect.

The function `EVP_PKEY_cmp_parameters()` compares the parameters of keys a and b.

The function `EVP_PKEY_cmp()` compares the public key components and parameters (if present) of keys a and b.

# NOTES

The main purpose of the functions `EVP_PKEY_missing_parameters()` and `EVP_PKEY_copy_parameters()` is to handle public keys in certificates where the parameters are sometimes omitted from a public key if they are inherited from the CA that signed it.

Since OpenSSL private keys contain public key components too the function `EVP_PKEY_cmp()` can also be used to determine if a private key matches a public key.

# RETURN VALUES

The function `EVP_PKEY_missing_parameters()` returns 1 if the public key parameters of pkey are missing and 0 if they are present or the algorithm doesn't use parameters.

These functions `EVP_PKEY_copy_parameters()` returns 1 for success and 0 for failure.

The function `EVP_PKEY_cmp_parameters()` and `EVP_PKEY_cmp()` return 1 if the keys match, 0 if they don't match, -1 if the key types are different and -2 if the operation is not supported.

# SEE ALSO

EVP_PKEY_CTX_new, EVP_PKEY_keygen